Mosquito Control ENT/rsc-6

MOSQUITO CONTROL AROUND THE HOME AND IN COMMUNITIES By: Charles Apperson and Michael Waldvogel, Extension Entomology	Insect Note - ENT/rsc-6

Mosquitoes are important pests because their biting activity often interferes with outdoor activities and can transmit disease organisms to people and domestic animals. Most mosquitoes are active during twilight hours and at night; however, around the home, the mosquitoes that breed in discarded containers are active during the day. Mosquitoes need water to complete their life cycle. They can breed in almost any source of water. Pesticides are only a short-term solution to nuisance mosquito problems. Solving the problem effectively and safely requires:

Proper identification of the mosquito species.
Obtaining information about the biology and behavior of these particular species.
Locating and eliminating breeding sites, particularly artificial sites that may be as close as your own backyard.
Using appropriate chemical controls measures, including personal protection.

Mosquito Life Cycle

All mosquitoes have one common requirement--they need water to complete their life cycle. Some mosquitoes lay individual eggs on the sides of treeholes or discarded containers, or in depressions in the ground that will hold water. The eggs can lay dormant for several years. Some eggs will hatch when they are flooded by rainfall. Several flooding and drying cycles are usually required for all of the eggs to hatch that are laid by a particular female mosquito. Other mosquitoes lay eggs directly on the surface of water. The eggs are attached to one another to form a raft or the individual eggs float on the water. These eggs hatch in 24-48 hours releasing larvae that are commonly called "wrigglers" because you can often see the larvae wriggling up and down from the surface of the water. Generally, the larvae feed on microorganisms and organic material in the water, but some mosquitoes prey on the larvae of other mosquito species and are regarded to be beneficial. In about 7-10 days after eggs hatch, larvae change to the pupal or "tumbler" stage in preparation for adult life. Female mosquitoes begin to seek an animal to feed on several days after emerging from water. Male mosquitoes mate with females one to two days after the females emerge. Males do not bite, but they do feed on plant juices.

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MOSQUITO BREEDING SITES
Since mosquitoes need water to complete their life cycle, the source of a mosquito problem can be just about anywhere that water can collect. Farm ponds and lakes are typically not major mosquito breeding areas if they contain fish and are free of weeds, algae or floating debris in which mosquito larvae can hide. Municipal and farm animal waste lagoons may become breeding sites. Permanent natural bodies of water, such as swamps, usually contain a wide variety of predatory insects and fish that keep mosquitoes from reaching severe nuisance levels, although storms, such as hurricanes, may disrupt this system and allow mosquito populations to rise rapidly. In residential areas, our activities often create mosquito breeding sites or increase the production of mosquitoes in natural bodies of water. For example, road building and maintenance often impede the drainage of runoff from rainfall, creating a mosquito breeding site. Clogged drainage ditches along roads can become productive mosquito breeding sites. Logging and construction activities often leave tire ruts in the soil. These depressions are ideal breeding sites for "floodwater" mosquito species. Around the home, natural tree holes and man-made objects such as bird baths, boats, canoes, discarded tires, and plant pots collect rainwater and allow mosquitoes to breed literally right in our own backyard. Stagnant water in unused swimming pools becomes an ideal breeding site. You can help reduce mosquito populations by eliminating or properly maintaining these problem spots:

Empty or (preferably) discard containers, old tires, etc. that can hold stagnating water.
If you use barrels/containers to collect rainwater for watering gardens, cover them with screening to keep out mosquitoes. Keep the screens clear of debris.
Treat decorative ponds/pools with products containing the bacteria Bacillus thuringiensis israelensis.
Dump excess water from saucers under outdoor flower pots.
Flush the water out of bird baths at least twice weekly.
Store boats, canoes and other objects so that they do not collect rainwater. Remove water that collects in depressions in tarpaulins covering boats and other equipment or objects.
Cover or drain unused swimming pools.
Keep rain gutters free of leaves and other debris that prevent water from draining.
Correct drainage problems in your yard that allow rainwater to pool in lowlying areas.
Fill tree holes to keep them from being used as breeding sites by mosquitoes.
Remove debris (or report drainage problems) in ditches and culverts along private or public roadways.

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MOSQUITO CONTROL

Because some mosquito species can fly far from breeding sites, efforts by individuals to control mosquitoes on their property rarely succeed. A community-wide effort may be needed to reduce mosquitoes to tolerable levels. This may require the formation of a local mosquito control program to organize community-wide "clean up" efforts and to determine the need to treat breeding sites or to apply insecticidal sprays to control adults.

Repellents

Some personal protection from mosquitoes can be achieved through the use of insect repellents. Many of these products contain DEET (N,N-diethyl-m-toluamide). More recently, the Centers for Disease Control and Prevention added two repellents its list of recommended products. Select the desired formulation (e.g., lotion, aerosol spray or cream) containing the highest percent of active ingredient, as stated on the product label, and apply it to exposed skin. Repeated use of repellents over a short period of time is not recommended, especially for children and pregnant women. For additional information on repellent products, see the Insect Note ENT/rsc-5 - Insect Repellent Products

Candles containing oil of citronella are often used outdoors to repel mosquitoes from around decks and picnic tables. These products work best when there is relatively little air movement to disperse the chemical too quickly. Avoid splashing water on lit citronella candles.

Non-chemical Control Measures

Installing and maintaining tight fitting screens on doors and windows will help keep mosquitoes out of the home.

Bats and birds, such as Purple Martins, may consume mosquitoes as part of their diet. You can install nesting boxes around your property to attract these natural predators to the area. However, bear in mind that the feeding activity of insect-eating bats and birds may not be sufficiently selective to cause noticeable reductions in mosquito populations. Also, many of our major mosquito problems occur at night or dusk/dawn when birds are less active.

What Doesn't Work

Electrocutor traps ("bug zappers") placed out of doors are not effective in reducing or eliminating mosquito populations. Studies have shown that less than ¼ of 1% of the insects "zapped" in such devices were actually biting insects. The majority of the insects killed in electrocutor traps are actually beneficial in some form. Electronic mosquito repellers that emit high frequency sound to "repel" mosquitoes have not been shown to be effective.

Several types mosquito traps that use radiant heat and/or chemicals such as carbon dioxide or octenol to attract mosquitoes are now being marketed in the U.S. To date, there are no scientifically-based studies that prove that these traps are able to provide control of local mosquito populations. Some mosquito species, such as Asian tiger mosquito are not attracted to these particular chemical cues.

Similarly, claims that certain plants placed around a porch or deck will repel mosquitoes are not supported by any scientifically-based test results.

Chemical Control
Chemical control of mosquitoes primarily targets the adult. Outdoor foggers will keep mosquitoes away for several hours, but once the chemical dissipates, the mosquitoes return. Spraying thickets or shrubs along the perimeter of your yard helps reduce the population of mosquitoes that rest in these areas. Consult the NC Agricultural Chemicals Manual or your county Cooperative Extension Center for more information on selecting appropriate pesticides for use against mosquitoes.

Insecticides are available for controlling larvae, but their application in either large bodies of water or small artificial breeding sites can be difficult and expensive, particularly for an individual homeowner. Control programs targeting mosquito larvae are best left to trained individuals in county or local government agencies. Most of these chemicals are not selective and some may even harm beneficial insects and other non-target organisms. Furthermore, use of these chemicals will provide only temporary reduction in mosquito populations. Modifying or eliminating breeding sites is the only long-term solution to severe mosquito problems.

Homeowners wanting to treat small areas, such as bird baths, garden pools, etc, might want to try a bacterial insecticides that are available at many retail stores, garden centers and on-line garden suppliers. There are several products formulated as "donuts" ("dunks") or as granules that contain the bacterium Bacillus thuringiensis israelensis or "Bti". This bacterium kills mosquitoes, but does not harm fish, birds or other wildlife. The "dunk" versions are well-suited for small breeding sites (100 sq. ft. or less) and will control mosquito larvae for about 30 days. Before using Bti products, you need information on the life cycle and habitat requirements of mosquitoes in your area. Simply treating all areas of standing water without knowing if they are actually sources of the problem is a waste of time and money.

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Mosquito Species Identification Since the habitat requirements of mosquito species are known, proper identification of the mosquitoes can be used to obtain information on where to search for and identify likely breeding sites. Collect some mosquito specimens for identification. Adult mosquitoes attempting to land are easily collected by placing a small jar (such as a baby food jar) over them. If possible, collect several dozen specimens. Place the jar in a freezer overnight. Spread the mosquitoes between sheets of facial or toilet tissue to protect them from being damaged, then place them back in the jar. Take the specimens to your county Cooperative Extension Service Center where arrangements can be made to identify the specimens and provide you with the information you need on how to control your mosquito problem.	Asian tiger mosquito Picture courtesy of P. Koehler, University of Florida
Individuals interested in mosquito identification can purchase the publication An Illustrated Key to the Larvae and Adult Mosquitoes of North Carolina and other Mid-Atlantic States (32 pages in length) through the Department of Communications Services. To order a copy, send $4.00 to: N. C. Cooperative Extension Service Publications Office, Box 7603 N. C. State University Raleigh, NC 27695-7603 Phone: (919) 513-3112 Fax: (919) 515-8602 Make your check payable to N. C. State University. Be sure to include your name and mailing address with your payment, and specify that your request is for publication AG-412.
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Click HERE for other sources of information about mosquito control and mosquito-borne diseases.

Pest information and control recommendations presented here were developed for North Carolina and may not be appropriate for other states or regions. Any recommendations for the use of chemicals are included solely as a convenience to the reader and do not imply that insecticides are necessarily the sole or most appropriate method of control. Any mention of brand names or listing of commercial products or services in the publication does not imply endorsements by North Carolina Cooperative Extension nor discrimination against similar products or services. All recommendations for pesticide use were legal at the time of publication, but the status of pesticide registrations and use patterns are subject to change by actions of state and federal regulatory agencies. Individuals who use chemicals are responsible for using these products according to the regulations in their state and to the guidelines on the product label. Before applying any chemical, always obtain current information about its use and read the product label carefully. For assistance, contact the Cooperative Extension Center in your county.

Distributed in furtherance of the acts of Congress of May 8 and June 30, 1914. North Carolina State University and North Carolina A&T State University commit themselves to positive action to secure equal opportunity regardless of race, color, creed, national origin, religion, sex, age, or disability. In addition, the two Universities welcome all persons without regard to sexual orientation. North Carolina State University, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.

Last updated - 8/04

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Mosquito Life Cycle

Repellents

Mosquito Species Identification